Implement clojure.core/sort

[jeaye]

We currently have this:

(defn sort
  "Returns a sorted sequence of the items in coll. If no comparator is
  supplied, uses compare.  comparator must implement
  java.util.Comparator.  Guaranteed to be stable: equal elements will
  not be reordered.  If coll is a Java array, it will be modified.  To
  avoid this, sort a copy of the array."
  ([coll]
   (sort compare coll))
  ([#_java.util.Comparator comp coll]
  ;;  (if (seq coll)
  ;;    (let [a (to-array coll)]
  ;;      (. java.util.Arrays (sort a comp))
  ;;      (with-meta (seq a) (meta coll)))
  ;;    ())
   (throw "TODO: port")))

The Clojure JVM version is included in there. As we can see, the collection is put into an array, the array is sorted, and then we return a sequence (carrying over the meta from the collection).

References

• Clojure is using this sort method: https://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#sort-java.lang.Object:A-
  • Note that it's a stable sort
• C++ has a stable sort too: https://en.cppreference.com/w/cpp/algorithm/stable_sort

Steps

• Add a object_ptr sort(object_ptr coll); to runtime/core/seq.hpp
• Implement it in runtime/core/seq.cpp
• Use visit_seqable to get a seqable, turn it into a seq, and then fill up a native_vector<object_ptr>
• Use std::stable_sort on the vector
• Return a native_vector_sequence box which takes ownership of the sorted vector
• Use core_native.cpp to add an intern_fn call to wrap your sort fn
• Update clojure/core.jank to forward the clojure.core-native/sort def

[bpiel]

I'll take this.

[jeaye]

Done in #218.